Field of the Invention
The present invention relates to a stop mechanism. More particularly, the present invention relates to a stop mechanism including a configuration for preventing light leakage from portions other than a portion corresponding to a stop effective diameter defined by stop blades, and to a lens apparatus using the same, and an image pickup apparatus.
Description of the Related Art
As stop mechanisms of related-art lens apparatus, there is known a configuration in which stop blades are each enlarged at a radially outer portion so that the stop blades are overlapped with each other in order to prevent light leakage from portions other than a portion corresponding to a stop effective diameter, which is caused when an aperture diameter of the stop mechanism is reduced from a maximum aperture position.
In Japanese Patent Application Laid-Open No. 2011-191490, there is disclosed a state in which light is not leaked from portions other than a portion corresponding to the stop effective diameter due to the overlap of stop blades 2 when the stop aperture diameter is reduced (state of FIG. 2(A)).
Further, in Japanese Patent Application Laid-Open No. 2011-191490, there is disclosed a configuration in which an operation lever 32 integrally formed on an operating member 3 configured to control movement of the stop blades 2 is moved on an outer peripheral side of the stop blades 2. With this, even when the operation lever 32 is projected in a direction of the stop blades 2, the stop blades 2 and the operation lever 32 do not interfere with each other. Consequently, as disclosed in FIG. 9, optical components L2 and L3 can be arranged in a holding frame 13 irrespective of the direction in which the operation lever 32 is projected, thereby increasing the degree of freedom in arrangement of the stop mechanism in the lens apparatus.
Still further, in Japanese Patent Application Laid-Open No. H05-113591, there is disclosed a configuration using a first diaphragm group for defining the stop effective diameter and a second diaphragm group for preventing the light leakage in order to reduce a diameter of the stop mechanism in the lens apparatus.
In Japanese Patent Application Laid-Open No. 2004-294678, there is disclosed a configuration of a stop mechanism in which parts of the stop blades (light leakage light prevention projections) are to be projected outward from a sleeve configured to receive the stop blades at the maximum aperture, thereby preventing the light leakage from portions other than a portion corresponding to the stop effective diameter and reducing the size of the stop mechanism.
However, in the related art disclosed in Japanese Patent Application Laid-Open No. 2011-191490, the operation lever 32 integrally formed on the operating member 3 is moved on the outer peripheral side of the stop blades, thereby increasing the diameter of the stop mechanism including a movable range of the operation lever 32. With this, the lens apparatus accommodating the stop mechanism may be increased in size.
Further, in Japanese Patent Application Laid-Open No. H05-113591, the diameter of the stop mechanism can be reduced, but structure of the stop mechanism is complicated, which may increase costs and difficulty in assembly.
In the configuration of Japanese Patent Application Laid-Open No. 2004-294678, the light leakage prevention projections are projected outward from the sleeve configured to receive the stop blades, and hence the configuration requires an operating portion configured to rotate a cam having cam grooves formed therein while preventing interference with the projected light leakage prevention projections. Thus, the size reduction in an optical axis direction is limited, and arrangement in the lens apparatus is restricted.